Piston grinding attachment



Oct. 29, 1968 R. E. PRICE ET Al. 3,407,541

y PISTON GRINDING ATTACHMENT I Filed sept. l14., 1965 4 sheets-sheet 1mma/2S AATTORNEY R. E. PRICE ET AL PIsToN GRINDING ATTACHMENT Oct. 29,1968 y 4 Sheets-Sheet 2 Filed Sept. 14, 1965 INVENTORS RALPH E. PWCE c3\HAROLD EBALSIGER ORNEY Oct. 29, 1968 R. E. PRICE ET AL 3,407,541

PISTON GRINDING ATTACHMENT Filed sept. 14, 1965 4 sheets-Sheet s IIIIIIINVENToRs ORNEY Oct. 29, 1968 R. E. PRICE ETAL PISTON GRINDINGATTACHMENT 4 sheets-shed A4:

Filed sept. 14, 1965 m w m/ MN5) Y mp@ .W me v D L T wwf n L Ann RHY/United States Patent() 3,407,541 PISTON GRINDING ATTACHMENT Ralph E.Price and Harold E. Balsiger, Waynesboro, Pa., assignors to Landis ToolCompany,-Waynesboro, Pa. FiledSept. 14, 1965, Ser. No. 487,156

8 Claims. (Cl. 51-101) `ABSTRACT OF THE DISCLOSURE differs from theconventional piston grinder, in that, the

axis of oscillation intersects the axis of rotation of the work drivespindle and` workpiece :and the oscillating 'Y 'movement of theworkpiece occurs about the intersection of the two axes as well as aboutthe axis of oscillation. It is this angular relation between the twoaxes which provides the tapered portion of the contour of the workpiece.

.- The present invention relates to apparatus for grinding non-circularworkpieces, particularly automotive pistons having a form generallyreferred to as tapered elliptical.

In a tapered elliptical piston, the degree of taper i' changesprogressively between arcuately spaced points on the skirt of thepiston. The small diameter at the head end of the skirt is smaller thanthe small diameter atthe open end of the skirt.

In order to form this type of piston by a grinding or other machiningoperation, the piston must be oscillated toward and from the cuttingtool about a predetermined point with relation to the piston, preferablya point on its Y axis.

In thelpas't, this type of piston has been ground on more or lessconventional grinding machines provided with an attachment whereby theswivel table is oscillated about the vertical swivel stud provided forswivelling the table for taper grinding. The piston is rotatablyAsupported im saidtable between a headstock center and a footstockcenter in, a position longitudinally spaced from the axis of the swivelstud. Oscillation of the piston about said swivel stud axis by aneccentric or master cam during a grinding operation, provides thedesired taper on the skirt of the piston. This is a progressivelyvarying taper and, therefore, :at each degree of rotation, the skirt ofthe oscillating piston is at a different angle to the face of thegrinding wheel. t

The oscillation of the piston toward and from a grind` I ing wheel is inatsubstantially horizontal plane between two-positions, in one of whichthe surface of the piston skirt may be parallel or at a slight angle tothe face of the grinding wheel, and'in the other position, at a greaterangle to the face of the grinding wheel. The range ofi oscillation isdetermined by the difference between the maximum and minimum diametersofthe master cam.

The principal disadvantage of this attachment is that it requiresmovement of a relatively large mass consistingl t of the swivel table,headstock and footstock mounted thereon about a mechanical pivot, andthe corresponding forces required to overcome as well as to resistinertia.

Itis, therefore, wan object of the present invention to provide improvedmeans for oscillating a workpiece relaice Ratented Oct. 29, 1968 tive toa cutting tool to produce a tapered elliptical form on said workpiece..A

Another object `is to provide a compact attachment for machining taperedelliptical workpieces.

. Another object i's'to provide apparatus in which only the work drivespindle and its immediate support are oscillated.

FIG. l is a front=elevation, partly in section.

FIG. 2 is a right handI end elevation.

FIG. 3.is aplan view. i

- FIG. 4 is a diagrammatic sketch showing the relation between themaster cam, follower, workpiece and grinding wheel. l A' This inventionprovides a simplified mechanism for grinding a tapered elliptical formon a workpiece vwhile utilizing fewer and lighter parts than previousapparatus used for this purpose. It utilizes the apparatus disclosed inco-pending application, Ser. No. 285,985, filed June 6, 1963, now U.S.Patent 3,247,619, granted Apr. 26, 1966, to which reference may be madeto details of structure and operation.

The apparatus disclosed in this application is modified in a novelmanner to provide the oscillating movement necessary to produce thetapered elliptical form on the workpiece. The vertical mechanical pivotwhich is an essential element of the old apparatus is eliminated, butits function is retained in the stationary or non-oscillating point onthe piston axis. The relatively large llat oscillating bearing surfaceof the'work table on the carriage of the old-type machine is replaced bythe relatively small cylindrical cradle pivot shaft of the abovementioned application. The modification of the device disclosed in theapplication consists in mounting the cradle pivot shaft at an angleinstead of parallel to the work drive spindle. The angle of the pivotshaftmust be such that the axis of the pivot shaft intersects the axisof the piston at a predetermined point about which the piston oscillatestowardand from the grinding wheel to produce the required taper on thepiston skirt. E v

' The reduction in the mass to be oscillated is due in large part of theelimination of a footstock and swivel table which, in turn, is due tothe use of `an improved chuck, whereby the workpiece is supported onlyat the head end. Supporting the workpiece only at the head end alsoeliminates deformation of the workpiece which oc- `lcurs when theworkpiece is supported between a headstock anda footstock. t

In the drawings, the work drive or headstock spindle 10 is rotatablysupported in bearings 11 in spindle housing 12. Spindle housing 12 ismounted for longitudinalv adjustment on a cradle 13. Cradle 13 isarranged to be supported by pivot shaft 14 in pivot shaft base 15.

Pivot shaft base 15 is arranged.. to support pivot shaft 14 at apredetermined angle relative to spindle 10. Base 15 is mounted forlongitudinal movement with cradle 13 :between bed 16 and spindle housing12 to provide` for slight adjustment of point X where axis P of pivotshaft v14 intersects the axis S of spindle 10 and workpiece W.

The location of point X relative to workpiece W along with the lift ordrop of a master cam, determines the amount or degree of taper to beground on said workpiece.

This adjustment provides for accurate positioning of pivot point X atassembly and also for pistons of different taper within the range ofadjustment.

Spindle 10 is driven through a suitable belt and pulley arrangement bythe motor 30t Master cam 20 on spindle i 10 has a contour which-includesa lift substantially greater than thatfto be applied to workpiece W.Follower roller 21 is supported on a pivoted arm 50 for contact with themaster cam 20. Arm 50 is pivoted at a point (not shown) near its upperend so that the oscillating movement of the follower roller Z1 inresponse to the rotation of master cam 20 is substantially reduced. Thisreduced movement is transmitted through a leaf spring 51 and a liexiblemember 52 to bracket 53 attached to cradle 13. Cradle 13 is mounted vforoscillation on shaft 14. Thus, any error in the contour of master cam 20is reduced by the lever ratio in arm 50 before it is transmitted toworkpiece W.

The means for rotatably supporting workpiece W in operative relationwith grinding wheel 25 consists of a chuck 40 arranged to grip the headportion of workpiece W in such a manner that the gripping force is nottransmitted to the portion of the workpiece being ground. Chuck 40 isthe sole means for supporting workpiece W during a grinding operation,thus eliminating the need for-a conventional footstock support memberwhich applies a holding ypressure to the portion of thevworkpiece beingground with the result that the workpiece is deformed during a grindingoperation with a correspondingerror in the contour of the finishedworkpiece.

The location of the intersection of the axis of workpiece W and the axisof oscillation of the workpiece and spindle 10, is determined by thefollowing equation:

AL Z-A-B where B is the lift or difference in radius at the large end 2of the piston skirt, and v L is the distance between points 1 and 2 atwhich dimensions A and B are measured.

Operation Rotation of spindle 10, master cam 20 and workpiece W by motor30 causes said parts to oscillate in a manner determined by the angularposition of pivot shaft 14 so that the left or head end of workpiece Wmoves through a greater distance toward and from grinding wheel 25 thanits right or open end.

At one limit of oscillation, the surface of workpiece W is parallel tothe face of grinding wheel 25 or at a slight angle thereto, depending onthe location of the zone of oscillation. As workpiece W moves towardgrinding wheel 2S about the swivel point X (FIG. 4), the angularrelation between workpiece W and grinding wheel 25 changes progressivelyso that at each degree of rotation, workpiece W is ground to a differenttaper. The maximum taper is produced when workpiece W reaches the limitof its oscillation toward grinding wheel 25.

' We claim:

1. In a machine for grinding non-cylindrical workpieces,

(a) a grinding wheel,

(b) a work support comprising (c) ahousing, l

(d) a work drive spindle rotatably mounted in said housing,

(e) means on said spindle for rotatably holding a workpiece in operativerelation with said grinding wheel, (f) a master cam on said spindle, (g)a follower roller for engaging the contour of said master cam, l

(l1) a cradle for supporting said housing and spindle for oscillation inresponsse to rotation of said master cam against said follower roller,

(i) the axis of oscillation of said cradle being at an angle to the axisof said spindle. 2. In a machine for grinding non-cylindricalworkpieces,

(a) a grinding wheel,

' (b) a work support comprising (c) a housing,

4 (d) a work drive lspindle rotatably'mounted in said housing,

(e) means on said spindle for rotatably holding a workpiece in operativerelation with said grinding wheel,

(f) a master cam on said spindle,

(g) a follower roller for engaging the contour ot said master cam,

(h) and'means -for grinding a tapered elliptical surface on saidworkpiece comprising (i) a cradle for supporting said housing andspindle for oscillation in response to rotation of said master camagainst said follower roller, y i

(j) the axis of oscillation of said cradle intersecting the axis of saidspindle at a predetermined position relative to said workpiece.

3. In a machine for grinding non-cylindrical workpieces, (a) a grindingwheel,

(b) a work support comprising (c) ahousing,

(d) a Work drive spindle rotatably mounted in said housing,

(e) means on said spindle for rotatably holding a workpiece in operativerelation with said grinding wheel,

(f) a master cam on said spindle,

(g) a follower roller for engaging the contour master cam,

(h) a cradle for supporting said housing and spindle for oscillation inresponse to rotation of said master cam against said follower roller,

(i) the axis of oscillation ofsaid cradle being at an angle less thanninety degrees to the axis of said spindle.

n 4. In a machine for grinding non-cylindrical workpieces,

(a) a grinding wheel,

(b) a work support housing,

(c) a work drive spindle rotatably mounted in said housing,

(d) means on said spindle for rotatably supporting a workpiece inoperative relation with said grinding wheel,

(e) a master cam on said spindle,

(f) a follower roller for engaging the contour of said master cam,

(g) means for oscillating said housing and spindle in response'torotation of said master cam against said follower roller,

(h) means to grind a tapered elliptical surface on said workpiececomprising (i) a support for said spindle mounted for oscillation aboutan axis at an angle to the axis of said spindle,

(1) said axes intersecting at a point determined by the of said equationwhere:

Z is the distance from the small end of the piston skirt to the point ofintersection of said axes; A is the lift or difference in radius betweenthe n major and minor axes at the small end of the pist-on skirt; f B isthe lift or difference in radius yat thelarge end of the piston skirt,and L is the distance between the points at which the dimensions A and Bare measured. 5. In a machine for machining tapered, non-cylindricalworkpieces, 1-

(a) a tool, n (b)v a work support comprising (c) ahousing, y l (d) aworkdrive spindle rotatably mounted in said housing, .v n' (e) means on saidspindle for rotatably holding a workpiece at one end only in operativerelation with said tool,

(f) a master cam on said spindle,

(g) a follower roller for engaging the contour of said master cam,

(h) a cradle for supporting said housing and spindle for oscillation inresponse to rotation of said master cam against said follower roller,

(i) the axis of oscillation of said cradle intersecting the axis of saidworkpiece.

6. In a machine for machining tapered, non-cylindrical workpieces,

(a) a tool,

(b) a Work support comprising (c) a housing,

(d) a work drive spindle rotatably mounted in said housing,

(e) means on said spindle for rotatably holding a workpiece at one endonly in operative relation with said tool,

(f) a master cam on said spindle,

(g) a follower roller for engaging the contour of said master cam,

(h) a cradle for supporting said housing and spindle for oscillation inresponse to rotation of said master cam against said follower roller,

(i) the axis of oscillation of said cradle intersecting the axis of saidworkpiece at a point in space which determines the taper to be producedon said workpiece.

7. In a machine for grinding non-cylindrical Workpieces,

(a) a grinding wheel,

(b) a work support housing,

(c) a work drive spindle rotatably mounted in said housing,

(d) means on said spindle for' rotatably supporting a workpiece inoperative relation with said grinding wheel,

(e) a master cam on said spindle,

(f) a follower roller for engaging the contour of said master cam,

(g) means for oscillating said housing and spindle in response torotation of said master cam against said follower roller,

(h) and means to grind a tapered elliptical surface on said workpiececomprising (i) a support for said spindle mounted for oscillation aboutan axis at an angle less than ninety degrees to the axis of saidspindle.

8. A machine for grinding a non-cylindrical workpiece comprising (a) awork support for holding a workpiece in operative relation to a grindingwheel,

('b) said support including workpiece holding means on a work drivespindle rotatably mounted in a housing,

(c) means for oscillating said housing and spindle including a mastercam on the spindle and engaging, by its periphery, a cam follower, and

(d) a pivot shaft pivotally supporting the master cam and spindle,

(e) the axis of the pivot shaft -being at an angle to the axis of thespindle.

References Cited UNITED STATES PATENTS 138,825 5/1873 Weiss 51--1012,037,796 4/1936 Johnston et al. 51-101 2,179,213 11/1939 Green 51-1012,559,534 7/1951 Green 51-101 2,599,987 6/1952 Green 51-101 3,247,6194/1966 Price et a1. 51-101 LESTER M. SWINGLE, Primary Examiner.

